PLEASE NOTE:
*
CCNet 90/2002 - 26 July 2002
-----------------------------
"We are in the midst of an orgy of misinformation and
confusion in
the press, concerning asteroid 2002 NT7."
--David Morrison, NEO News (07/25/02)
"It's the old train on the track problem," Dr. Donald
K. Yeomans of
the Jet Propulsion Laboratory said. "You don't know when the
train is
going to arrive at the crossing point.
After 2019, NT7 will have several more close passes by Earth,
including 2044, 2053, 2060 and 2078. Dr. Yeomans said that with a
few
more weeks of observations, astronomers will probably be able to
rule out
any chance of impact for all of them."
--Kenneth Chang, The New York Times, 25 July 2002
"Thus, [Gareth] Williams notes, the public is likely to see
additional warnings first raised then lowered as search efforts
turn
up new asteroids and comets. Though astronomers are concerned
about
being seen as "crying wolf," they say they would rather
provide initial
information and later ease a warning than face accusations that
they
withheld information if an asteroid turns out to have Earth in
its
crosshairs."
--Peter N. Spotts, The Christian Science Monitor, 26 July
2002
(1) ASTEROID 2002 NT7
JPL, 24 July 2002
(2) ASTRONOMERS WARN OF POSSIBLE HIT BY NEW-FOUND ASTEROID
The Christian Science Monitor, 26 July 2002
(3) NEW ASTEROID HAS LONG ODDS FOR EARTH CRASH
The New York Times, 25 July 2002
(4) NASA RE-ASSURANCE: CAVEAT IMPACTOR
NASA Science News for July 26, 2002
(5) CHINESE NEWS AGENCY: "SLIM CHANCE OF ASTEROID COLLISION
WITH EARTH IN 2019"
Xinhua News Agency, 26 July 2002
(6) ASTEROID SCARE: THERE IS NO NEED TO PANIC
The Nation, 26 July 2002
(7) PERILS IN SPACE - LEMBIT OPIK, LIB DEM MP, ON WHY THE
GOVERNMENT MUST ACT
The Mirror, 25 July 2002
(8) IT'S NOT THE END OF THE WORLD - JUST YET
The Times, 25 July 2002
(9) ANOTHER PRESS AGENCY WIRE: "ASTEROID COULD HIT EARTH IN
2019:
SCIENTISTS"
Space Daily, 25 July 2002
(10) SIR PATRICK MOORE'S ADVICE OVER ASTEROID: "DON'T
PANIC" :-)
The Daily Record, 26 July 2002
(11) THANK HEAVANS, THIS ASTEROID WON'T COLLIDE WITH EARTH
North Jersey.com, 25 July 2002
(12) "AN ORGY OF MISINFORMATION AND CONFUSION CONCERNING
2002 NT7"
David Morrison <david.morrison@arc.nasa.gov>
(13) YOU SAY TORINO - I SAY PALERMO: WHY BLAMING THE MEDIA WON'T
WORK
Benny Peiser <b.j.peiser@livjm.ac.uk>
(14) THE MEANING OF ASTEROID RISK LISTINGS
Jon Giorgini <jdg@tycho.jpl.nasa.gov>
(15) DIFFERENT IMPACT PROBABILITIES?
Kelly Beatty <kbeatty@SkyandTelescope.com>
(16) NEAR MISSES AND THE MEDIA
Charles Cockell <csco@bas.ac.uk>
(17) GERMAN TV: "10% PROBABILITY OF IMPACT"
Daniel Fischer <dfischer@astro.uni-bonn.de>
(18) TRUE TALLY OF ASTEROIDS PROBABLY AT HIGH END OF ESTIMATES
Space.com, 23 July 2002
(19) SCIENTISTS DOUBT CLAIMS OF INVISIBLE 'MIRROR' COMETS AND
ASTEROIDS
Space.com, 25 July 2002
(20) AND FINALLY: 10 WAYS TO BEAT ARMAGEDDON :-)
The Sun, 25 July 2002
===========
(1) ASTEROID 2002 NT7
>From JPL, 24 July 2002
http://neo.jpl.nasa.gov/
Asteroid 2002 NT7 currently heads the list on our IMPACT RISKS
Page because
of a low-probability Earth impact prediction for February 1,
2019. While
this prediction is of scientific interest, the probability of
impact is not
large enough to warrant public concern.
Discovered on July 9, 2002 by the LINEAR team, asteroid 2002 NT7
is in an
orbit, which is highly inclined with respect to the Earth's orbit
about the
sun and in fact nearly intersects the orbit of the Earth. While
the orbits
of Earth and 2002 NT7 are close to one another at one point in
their
respective orbits, that does not mean that the asteroid and Earth
themselves
will get close to one another. Just after an asteroid like 2002
NT7 is
discovered, the limited number of observations available do not
allow its
trajectory to be tightly constrained and the object's very
uncertain future
motion often allows a very low probability of an Earth impact at
some future
date. Just such a low probability impact has been identified for
February 1,
2019 and a few subsequent dates. As additional observations of
the asteroid
are made in the coming months, and perhaps pre-discovery archival
observations of this object are identified, the asteroid's orbit
will become
more tightly constrained and the future motion of the asteroid
will become
better defined. By far the most likely scenario is that, with
additional
data, the possibility of an Earth impact will be eliminated.
This is an example of the type of scenario that we can expect as
some types
of near-Earth objects are discovered. For some objects, their
uncertain
initial orbits cannot be used to immediately rule out future very
low-probability Earth impacts, but when additional observations
are used to
refine the initial orbit, these low-probability Earth impact
possibilities
will go away. Other recently discovered near-Earth asteroids will
be added
to the Risk page until their orbits are refined and they are then
dropped
off the list of closely watched objects. This is how the system
is expected
to work and any initial indication of a low-probability Earth
impact
followed by a removal of that event from our IMPACT RISKS tables
should not
be considered a mistake. It is a natural result of the on-going
process of
monitoring the motions of near-Earth objects.
===========
(2) ASTRONOMERS WARN OF POSSIBLE HIT BY NEW-FOUND ASTEROID
>From The Christian Science Monitor, 26 July 2002
http://www.csmonitor.com/2002/0726/p02s02-stss.html
A new discovery highlights the need to focus worldwide efforts to
track
space matter.
By Peter N. Spotts | Staff writer of The Christian Science
Monitor
Astronomers worldwide are tracking a mile-wide chunk of space
rock to
determine if a close encounter with Earth projected for Feb. 1,
2019 will be
too close for comfort. Their efforts highlight what some
scientists see as a
need to focus scattered attempts to deal with threats from
asteroids and
comets, which have violently rewritten the history of life on
Earth over
billions of years.
On Wednesday, astronomers announced that asteroid 2002 NT7 has a
small
probability - less than 1 chance in 200,000 - of striking Earth
during its
2019 flyby. Researchers expect this probability to shrink as they
make more
observations and use new data to refine calculations of the
asteroid's position and orbit.
The asteroid was discovered July 9 by the LINEAR project, an
automated
search for near-earth asteroids conducted by the MIT Lincoln
Laboratory in
Lexington, Mass. The asteroid orbits the sun once every 2.4
years;
astronomers say if it struck Earth, it would pack the explosive
punch of 1.2
million megatons of TNT.
The asteroid's heft, uncertainties about its position, and the
relatively
short time for action if it proves dangerous have won it some of
the highest
initial hazard ratings ever for a newly discovered asteroid.
Still, "this object does not worry me in the least,"
says Gareth Williams,
assistant director of the International Astronomical Union's
Minor Planet
Center in Cambridge, Mass. He notes that several times over the
past few
years, astronomers have discovered asteroids that first appeared
to hold the
potential for a collision with Earth but later proved to pose
little or no
threat.
Crying 'Asteroid?'
The announcements of such discoveries might seem to be cases of
astronomers
crying, "Asteroid!," but Mr. Williams holds the process
"is perfectly
normal." As astronomers discover new asteroids, they
calculate their orbits
and their potential for impact with Earth. They then rate the
object on two
threat-rating systems developed over the past decade. Under both
systems,
astronomers see the chance that 2002 NT7 will collide with Earth
as
"extremely unlikely," but agree that it deserves close
monitoring.
To date, scientists have discovered roughly 500 near-earth
asteroids larger
than a kilometer across, but they estimate that there may
actually be up to
1,200 of them. Astronomers have placed a high priority on
building a new 6.5
meter telescope that could spot hundreds more.
Thus, Williams notes, the public is likely to see additional
warnings first
raised then lowered as search efforts turn up new asteroids and
comets.
Though astronomers are concerned about being seen as "crying
wolf," they say
they would rather provide initial information and later ease a
warning than
face accusations that they withheld information if an asteroid
turns out to
have Earth in its crosshairs.
Yet if efforts to discover new near-earth asteroids are ramping
up, efforts
to prepare for a verified threat are "haphazard" and
"unbalanced," says
Clark Chapman, a researcher in the office of space studies at the
Southwest
Research Institute in Boulder, Colo. Few policymakers are
prepared to
respond to such a warning.
But that may be changing. Earlier this month, representatives
from NASA, the
Minor Planet Center, the US Space Command, and others met with
House Space
Subcommittee chairman Dana Rohrbacher (R) of California on
Capitol Hill to
discuss challenges and opportunities for asteroid-hazard
mitigation.
Two approaches often discussed are: using some kind of rocket
motor to
deflect the asteroid, or - as a last resort - blowing it up
before it
reaches Earth. Dr. Chapman and colleagues Daniel Durda and Robert
Gold have
noted that before taking either of those steps, researchers must
discover
its composition and other characteristics. They propose placing
small
reconnaissance craft on orbit early, to shorten the time between
alerts and
scoiting missions. (Currently, it can take 18 to 24 months to
launch such a
mission.) Spacecraft designed to deflect or destroy asteroids
also could be
set on orbit to shorten response time. The trio estimates that
with 30
years' warning, a space shuttle main engine could deflect a
1-kilometer-class asteroid.
For larger objects at shorter notice, explosives may be the only
option, but
this technique could lead to Earth's bombardment by asteroid
fragments,
which could prove more risky than a single, large impactor.
"You can't go
blindly in and nuke the thing as it comes by," Williams
says.
Unexpected consequences
Yet large impactors may not be the most serious immediate threat.
In June,
when the India-Pakistan crisis was at its height, US
early-warning
satellites caught a bright flash over the Mediterranean Sea - a
burst that
released enough energy to match the atomic bomb that leveled
Hiroshima,
according to Brig. Gen. Simon Worden, deputy director of
operations for the
US Space Command. The cause: an asteroid, perhaps five to 10
meters wide.
Had the burst occurred at the same latitude a few hours earlier,
"the
results on human affairs might have been much worse," since
Pakistan and
India lack the sensors to distinguish between an asteroid and a
nuclear
explosion.
"This situation alone should be sufficient to get the world
to take notice
of the threat of asteroid impact," he says.
Copyright 2002, The Christian Science Monitor
=============
(3) NEW ASTEROID HAS LONG ODDS FOR EARTH CRASH
>From The New York Times, 25 July 2002
http://www.nytimes.com/2002/07/25/science/25ASTE.html
By KENNETH CHANG
A newly found asteroid, large enough to wreak worldwide
destruction, will
cross Earth's path in 2019, and although the chance of a
collision is slim,
astronomers cannot yet rule it out.
If the asteroid, named 2002 NT7, were to hit, it would be on Feb.
1, 2019.
The odds of that happening are less than 1 in 200,000, NASA's Jet
Propulsion
Laboratory said yesterday. That is roughly the same chance that
an unknown,
as yet unseen meteor will hit Earth between now and then.
Scientists expect
the 1-in-200,000 odds to grow longer as they learn more about the
asteroid's
orbit.
On the 0-to-10 Torino scale describing asteroid hazards, 2002 NT7
ranks a 1,
meriting careful monitoring but with the chance of impact judged
extremely
unlikely. A ranking of 0 means no danger; a 10 means certain
impact with
worldwide devastation.
In earlier asteroid scares, astronomers quickly ruled out any
chance of
impact, or the potential impact remains so far in the future that
it is
impossible to judge the risk.
Astronomers first spotted 2002 NT7 on July 9. With two weeks of
observations, they have mapped out its orbit fairly precisely -
it circles
around the Sun once every 837 days at a steep tilt of 42 degrees
compared to
the orbits of the planets.
But astronomers have not yet pinned down the asteroid's location,
which
means their predictions of where it will be on Feb. 1, 2019, may
be off by
tens of millions of miles.
"It's the old train on the track problem," Dr. Donald
K. Yeomans of the Jet
Propulsion Laboratory said. "You don't know when the train
is going to
arrive at the crossing point."
If NT7, which is one-and-one-quarter miles wide, does strike
Earth at 60,000
miles an hour, the impact could gouge a crater many miles wide,
destroying
large swaths of the surrounding area.
On average, an asteroid of NT7's size hits Earth every few
million years.
The meteor that killed off the dinosaurs 65 million years ago was
6 to 9
miles wide.
After 2019, NT7 will have several more close passes by Earth,
including
2044, 2053, 2060 and 2078. Dr. Yeomans said that with a few more
weeks of
observations, astronomers will probably be able to rule out any
chance of
impact for all of them.
Copyright 2002 The New York Times Company
see also ASTEROID WILL CROSS EARTH ORBIT
The International Herald Tribune, 26 July 2002
http://www.iht.com/articles/65724.html
===========
(4) NASA RE-ASSURANCE: CAVEAT IMPACTOR
>From NASA Science News for July 26, 2002
http://science.nasa.gov/headlines/y2002/26jul_nt7.htm?list20392
An asteroid with almost no chance of hitting Earth made big
headlines this
week.
July 26, 2002: I slid a dollar bill across the counter, and the
cashier
handed back a lottery ticket. The odds for winning: 1-in-250,000.
A long
shot, but you never know.
Walking out of the store, ticket in hand, I glance at a
newspaper. "Tony
Phillips wins the lottery!" the headline declared. Gosh, I
thought, that
seems premature ... not to mention weird.
Indeed, it's fiction. For one thing, I never buy lottery tickets.
But
mainly, no one would write such a headline based on such slender
odds.
Yet that's what happened this week, in real life, to an asteroid.
On July 9, 2002, MIT astronomers discovered 2002 NT7, a 2 km-wide
space rock
in a curious orbit. Unlike most asteroids, which circle the Sun
in the plane
of the planets, 2002 NT7 follows a path that is tilted 42
degrees. It spends
most of its time far above or below the rest of the solar system.
Every 2.29
years, however, the asteroid plunges through the inner solar
system not far
from Earth's orbit.
After a week of follow-up observations, researchers did some
calculations.
There was a chance, they concluded, that 2002 NT7 might hit our
planet on
February 1, 2019. The odds of impact: 1-in-250,000.
"Space Rock 'on Collision Course'," a headline declared
days later.
"Asteroid Could Wipe Out a Continent in 2019," another
one warned. Really.
"In fact," says Don Yeomans, the manager of NASA's
Near-Earth Object Program
at JPL, "the threat is minimal. One-in-250,000 is a very
small number."
The odds are not only low, but also uncertain. Yeomans explains:
"We've been
tracking 2002 NT7 for a very short time--only 17 days so
far," Meanwhile,
the asteroid takes 2.29 years to orbit the Sun. Predictions based
on such a
small fraction of an orbit are seldom trustworthy.
It's becoming a familiar routine: Astronomers discover a
near-Earth
asteroid. With only meager data at hand, they can't rule out a
collision in
the distant future. Headlines trumpet the danger. Finally, the
alarm
subsides when more data lead to a better orbit--one that rules
out an
impact.
"As far as the public is concerned," says Jon Giorgini
of JPL's Solar System
Dynamics Group, "it just isn't worth getting worked up about
an object with
a couple weeks of data showing a possible Earth encounter many
years from
now. Additional measurements will shrink the uncertainty by a
large
amount--and Earth will (almost certainly) fall out of the risk
zone."
Already this is happening for 2002 NT7. The calculated
probability of a
collision with Earth is shrinking as astronomers add new data
each day. "I
suspect it will take only a few more weeks (or maybe months) to
completely
rule out an impact in 2019," says Yeomans.
Giorgini explains further: "When we calculate an asteroid's
position (based
on measurements made at a telescope), the result isn't a single
point in
space. Instead, it's a volume of space where the asteroid could
be with some
probability. We deal with probabilities, not absolute answers,
because the
measurements contain errors." For example, optical data can
be corrupted by
twinkling and refraction in Earth's atmosphere. (Radar is better,
notes
Giorgini, but no radar data have yet been obtained for 2002 NT7.)
"When you project this initial probability region years into
the future, it
naturally expands. For a newly discovered object with only a few
days
tracking, the uncertainty region can easily grow to cover a big
part of the
inner solar system. Because Earth is in the inner solar system,
and can
potentially cut through this volume of smeared out probability,
we end up
with finite impact probabilities."
"A finite probability, however, is not really a prediction
of impact," he
cautions, "but a statement that one is possible." Of
course, many things are
possible. Like the newspaper headline "Tony Phillips wins
the Lottery!" But
most of them do not happen.
JPL lists asteroids like 2002 NT7 on their Internet "risk
page" not to raise
an alarm, says Yeomans, but to alert astronomers when new
discoveries merit
attention. "It's important that we continue tracking these
asteroids to
refine their orbits," he says. The more observers, the
better.
Above: Astronomer John Rogers captured this image of 2002 NT7,
faint and far
away, on July 23, 2002, using a 0.3-meter telescope at the
Camarillo
Observatory.
What's an ordinary person to do?
The next time you see a headline "Killer asteroid threatens
Earth!" ask
yourself two questions: Have we known about this space rock for
more than a
week or so? (If not, check again in a month. It probably won't be
considered
a killer then.) And what are the odds of impact?
If you're more likely to win the lottery, there's probably
nothing to worry
about.
see also: ANIMATED GIF OF THE MOTION OF ASTEROID 2002 NT7
http://www.klet.org/2002nt7.html
===============
(5) CHINESE NEWS AGENCY: "SLIM CHANCE OF ASTEROID COLLISION
WITH EARTH IN 2019"
>From Xinhua News Agency, 26 July 2002
BEIJING, Jul 26, 2002 (Xinhua via COMTEX) -- Leading Chinese
astronomers
have said they see "little chance" of an asteroid
collision with the earth
in 2019, and refute some of the recent unsupported reports on the
issue.
Overseas media recently reported a two-kilometer wide asteroid,
dubbed 2002
NT7, could collide with the earth on February 1, 2019.
"Such reports are irresponsible," said Jiang Xiezhu,
vice president of
China's National Astronomical Observatories (NAO), in an
exclusive interview
with Xinhua.
The asteroid was seen through a New Mexico telescope in the
United States on
July 9 by astronomers from the Lincoln Near Earth Asteroid
Research Project.
It was then about 135 million kilometers from the earth and was
estimated to
be on a 837-day trajectory around the sun, said Jiang.
Doctor Zhu Jin, a NAO researcher, said two weeks of observation
was simply
not enough to figure out the asteroid's potential path.
"It needs further observation but poses no threat at the
moment, " he said.
"Not until more observation data enables scientists to
narrow down its
estimated trajectory can any predictions be made."
Astronomers worldwide have observed 375,000 asteroids since the
first was
discovered by Italian astronomers in 1801.
They have worked out the precise trajectories for 44,000 of these
asteroids,
none of which is likely to pose any real threat to the earth in
the near
future, said Zhu.
Copyright 2002 XINHUA NEWS AGENCY.
==========
(6) ASTEROID SCARE: THERE IS NO NEED TO PANIC
>From The Nation, 26 July 2002
http://www.nationmultimedia.com/page.news.php3?clid=3&id=2677&usrsess=1
Thai astronomers join rush to reassure public that possibility of
impact is
small
Astronomers told Thais yesterday not to panic over reports that a
giant
asteroid may hit Earth in 2019 because the chances of a collision
are very
small.
Even if the recently discovered asteroid is heading towards Earth
a
collision can be prevented, they said.
While it would take relevant agencies several years to work out a
collision-prevention plan, the discovery was made 17 years in
advance,
greatly reducing the risk of impact, said Worawit Tanwuttipundit,
a member
of the Thai Astronomy Association's board.
Nasa astronomers discovered a two-kilometre-wide asteroid, dubbed
2002 NT7,
on July 9 when it was 135 million kilometres from Earth.
Astronomers
forecast the asteroid has a one in 250,000 chance of hitting the
Earth on
February 1, 2019. A collision could cause a global catastrophe.
Astronomer Dr Chaiwat Khupatakul said Thais should not be
frightened by the
reports. Although the two-kilometre width of the asteroid is
considered huge
and could cause a global catastrophe if it hit here, Chaiwat said
astronomers and scientists would be able to invent technologies
to prevent
the collision.
Collision could be prevented either by destroying the asteroid
with nuclear
or chemical missiles or drawing another asteroid in to hit 2002
NT7, said
Chaiwat.
There are believed to be millions of asteroids in the region of
space
between Mars and Jupiter, although astronomers have only
catalogued about
500 of them.
On July 9, astronomers with the Lincoln Near Earth Asteroid
Research Project
in the United States discovered the asteroid, which is in orbit
around the
Sun, through a New Mexico telescope.
More than 100 follow-up observations allowed astronomers to
calculate six
other potential impact dates in 2044, 2053, 2060 and 2078. Were
the paths of
2002 NT7 and the Earth to cross, the asteroid would strike the
Earth with
the explosive energy of 1.2 million megatons of TNT, according to
the Jet
Propulsion Laboratory in the US.
Last month, an asteroid the size of a soccer field missed the
Earth by
120,675km in one of the closest known approaches by an object
that size.
Sukanya Lim
Copyright 2002, THE NATION, AP
=============
(7) PERILS IN SPACE - LEMBIT OPIK, LIB DEM MP, ON WHY THE
GOVERNMENT MUST ACT
>From The Mirror, 25 July 2002
WHEN I first brought the subject up in the House of Commons in
1998 it was
met with spiteful laughter. I'm glad to say that the same people
are not
laughing any more.
If asteroid 2002 NT7 did hit the Earth it could wipe out a
quarter of the
human population.
The chances of something eventually making an impact on Earth are
100 per
cent - we just don't know when it will be.
I have fronted a Parliamentary campaign calling for the
government to take
the outer-space threat seriously for the past four years.
Scientific experts have campaigned since the mid-1990s and were
inspired by
Arthur C Clarke, considered to be the greatest science fiction
writer of all
time, who first coined a phrase "Spaceguard," his
fictional early warning
system that detected objects hurtling through space.
Astronomers were concerned about the possibility, but the
government was not
taking their concerns seriously.
We are calling for them to do two things. We want a proper
tracking campaign
put in place, using a network of six or seven telescopes around
the world
that would cover just about every quarter of space. And we need
to develop
something to stop an asteroid that's coming our way reaching us.
That may
sound like science fiction, but it's actually science fact.
The resources are already available to us. We could use a nuclear
weapon, a
rocket or a solar sail to deflect the object. The latter sounds
exotic and
has not yet been tested, but it is feasible. A solar sail would
use the
constant stream of particles from the sun to cause the asteroid
to sail off
in a different direction.
The money needed would be immense - about pounds 80million to
track the
objects and another pounds 4,000million to deflect it.
But this is peanuts when you consider that we're talking about
Armageddon.
Britain is already ahead of the rest of the world because of the
work that
the campaign has done. The Government commissioned a report to
see if there
was a threat and confirmed what we had been saying for a long
time ... that
there is a danger.
As a result they made 14 recommendations for action, including
improvements
on tracking and research.
But now I'm asking the Government to lead international action.
Tony Blair and George W Bush have a special relationship that
could be used
here. I would tell him to talk to Bush about an asteroid threat.
And I would ask the Government to give the astronomers the
resources to
carry out the necessary research, looking at asteroids and
finding out more
about what they are made of.
We must use the next G8 meeting to discuss the issue. It is very
serious and
just because it doesn't happen very often, it doesn't mean we
should ignore
it.
Tony Blair needs to be a key player. He took a stand against
terrorism and
can take a stand about this too.
An asteroid could do much more harm than terrorism can.
Copyright: MGN Ltd
===========
(8) IT'S NOT THE END OF THE WORLD - JUST YET
>From The Times, 25 July 2002
By Mark Henderson, Science Correspondent
AN ASTEROID big enough to obliterate Britain and devastate a
continent could
be on a collision course with Earth, making it the most
threatening object
yet detected in space, scientists said yesterday.
The space rock, 1.25 miles across and named 2002 NT7, will
approach our
planet in 2019, and there is a real, though remote, possibility
of an impact
that would release almost 750 million times as much energy as the
Hiroshima
atomic bomb.
The shock wave from such a strike would cause tsunamis (giant
waves) and
fires worldwide as well as a "nuclear winter" effect.
It would probably not,
however, be enough to wipe out all life on Earth.
Astronomers say that it is too soon to panic. They have
calculated that the
chance of a catastrophe is only 1 in 500,000. But an impact is
still 28
times more likely than a player has of winning the Lotto.
The asteroid was discovered on July 5 by the Linear Obervatory in
New
Mexico. Its orbit initially suggested an impact on February 1,
2019, but it
now appears that 2002 NT7 will instead pass the Earth at a
distance of about
32,000 miles - still a very near miss in cosmic terms.
Iwan Williams, Professor of Astronomy at Queen Mary, University
of London,
said: "This is the first that looks even vaguely
serious."
The best immediate strategy for dealing with the asteroid would
involve
nudging it out of orbit with nuclear weapons
Copyright 2002, The Times
=============
(9) ANOTHER PRESS AGENCY WIRE: "ASTEROID COULD HIT EARTH IN
2019:
SCIENTISTS"
>From Space Daily, 25 July 2002
http://www.spacedaily.com/news/020725120601.mgn9y1gk.html
LONDON (AFP) Jul 25, 2002
A potentially devastating asteroid could strike Earth in 2019,
according to
American and British scientists.
Astronomers in New Mexico spotted asteroid 2002 NT7 on July 5.
They
calculated that the asteroid, estimated between two and four
kilometres in
diameter, had a one in 60,000 chance of hitting Earth on February
1, 2019.
"Today, calculations show a one in 60,000 chance that the
asteroid will
strike the Earth," Alan Fitzsimmons, scientist at the
National Space Centre
in Leicester, central England, told The Guardian newspaper on
Thursday.
A British parliamentary deputy has urged the government not to
ignore the
threat.
Lembit Opik, from the Liberal Democrats, Britain's third biggest
party,
said: "I have said for years that the chances of this
asteroid having an
impact which could wipe out most of the human race is 100
percent.
"There's a good chance this particular object won't hit us
but we know that
a large object will hit us sooner or later. This is the closest
approach we
have seen so far."
The asteroid, travelling at 28 kilometres per second, could cause
tidal
waves, massive fires and volcanic activity, added Opik.
Asteroids are often described as the rubble left over from the
building of
the solar system.
They orbit the Sun, but the paths are never eternal, and their
trajectories
can be deflected by gravitational pull whenever the asteroid
passes by a
planet.
A football-pitch-sized asteroid capable of razing a major city
came within a
whisker of hitting the Earth on June 14.
Asteroid 2002 MN, estimated at up to 120 metres (yards) long,
hurtled by the
Earth at a distance of 120,000 kilometers (75,000 miles), well
within the
orbit of the Moon and just a hair's breadth in galactic terms.
It is the closest recorded near-miss by any asteroid, with the
exception of
a 10-metre (33-feet) rock, 1994 XM1, which approached within
105,000
kilometers on December 9, 1994.
All rights reserved. © 2002 Agence France-Presse
==============
(10) SIR PATRICK MOORE'S ADVICE OVER ASTEROID: "DON'T
PANIC" :-)
>From The Daily Record, 26 July 2002
http://www.dailyrecord.co.uk/news/page.cfm?objectid=12064002&method=full&siteid=89488
STARGAZER Patrick Moore took on the role of Dad's Army's Corporal
Jones
yesterday to tell worried millions: "Don't panic."
Scientists in the US - like Jonesey's Home Guard comrade Private
Frazer -
believe we're "all doomed" because of an asteroid on
collision course with
the Earth.
But veteran astronomer Moore says there's very little to worry
about,
despite the pessimistic predictions of the world being hit by an
Armageddon-like disaster in 2019.
Scientists in the US say the asteroid, more than a mile wide,
will wipe out
a continent if it hits the Earth.
That would cause massive climate change and wipe out life as we
know it.
The asteroid, a giant mass of ice and iron known as 2002 NT7, was
first
spotted a month ago by astronomers in New Mexico.
Since then, Sky at Night presenter Moore, 79, has been monitoring
its
trajectory as it hurtles through space towards our planet.
He said its chances of colliding with Earth were less than of
hitting the
lottery jackpot. And even if it is heading straight for us,
experts have 17
years to work out how to stop it.
He said: "I have been looking at this projectile for some
time and I am
telling everyone don't panic. The chances of this particular
asteroid
hitting the Earth are extremely unlikely - you would have a
better chance of
winning the lottery.
"Obviously, there is always a chance. But the fact this one
has been
detected early means measures can be taken to deflect it with a
nuclear
explosion if required."
Moore admits an impact would be devastating, adding: "It
would have similar
effects to the asteroid which supposedly wiped out the dinosaurs.
Very few
would survive and those that did would have to start again from a
second
Stone Age."
Copyright 2002, Daily Record
=============
(11) THANK HEAVANS, THIS ASTEROID WON'T COLLIDE WITH EARTH
>From North Jersey.com, 25 July 2002
http://www.bergen.com/page.php?level_3_id=25&page=4402264
By BOB GROVES
Staff Writer
As if the stock market and terrorism weren't enough to worry
about this
summer.
Astronomers say another newly discovered asteroid, several
football fields
wide, will miss the Earth next month - and not by much,
astronomically
speaking, at least.
What's more, it has a 1-in-500,000 chance of slamming into us the
next time
it's in the neighborhood - 20 years from now.
The asteroid, designated 2002 NY40, was discovered on July 14. It
should
sail within 330,000 miles of Earth - just outside the Moon's
orbit - on Aug.
17-18, astronomers say.
The hurtling piece of space rock is about 10 times larger than
the asteroid
that "narrowly" slipped past Earth - 75,000 miles away,
but inside the
Moon's orbit - June 14. That one wasn't noticed until three days
later in
astronomers' rear-view mirrors.
Asteroids are pockmarked mini-planets made of rock and iron. Most
of them
are orbiting the Sun harmlessly, in a belt between Mars and
Jupiter, whipped
around by Jupiter's massive gravity at speeds up to three miles
per second.
Others, like this one, follow more eccentric orbits, in some
cases crossing
the path of the Earth.
En route, it will appear to hang motionless in the sky - which
astronomers
say is the signature of a close-call asteroid, as it bears down
on Earth
from deep space.
The new asteroid is nowhere near as large as the killer comets
and meteors
that loomed in the recent movies "Armageddon" and
"Deep Impact" - or even
the one that threatened Springville on "The Simpsons"
TV cartoon.
The asteroid will increase its brightness about 3,000 times
during the next
three weeks as it travels here with the northern Milky Way in the
background
of the night sky. On the night of Aug. 17 - its closest approach
to Earth -
its motion will be visible through binoculars and small
telescopes. It will
appear about the size of a star or satellite, moving lazily for a
few hours,
high in the southeast sky, on a path that takes it beneath the
constellation
Cygnus.
"It certainly won't have the beauty or visual thrills of a
comet," said
Bruce Draine, a professor of astrophysics at Princeton University
and an
astronomer at the observatory there. "Meteor showers are
more aesthetically
pleasing. This object will just be a dot of light."
Wayne T. Hally, a meteor expert in High Ridge, agreed.
"People are not going
to see a flaming asteroid coming toward them, like you do in the
movies,"
said Hally, meteor research coordinator for the New Jersey
Astronomical
Association. "It's definitely not a naked-eye event."
The "thrill," if that word applies, of asteroid 2002
NY40 is contemplating
the destruction it would cause if it hit the Earth, Draine said.
The
asteroid, which is estimated to be between one-third and one-half
mile wide,
would pack the explosive punch of a 50,000- to-100,000-megaton
bomb, Draine
said.
"To put it on a scale of badness, it would not be a happy
day," he said. "So
an event like that would be catastrophic, especially if it
happened with
little or no advance warning.
"The amount of energy released would be much greater than
the entire nuclear
arsenals of East and West. Even if it happened in the ocean near
populated
areas, it would produce tidal waves that would be devastating
disasters," he
said.
An asteroid which is believed to have exploded above Tunguska,
Siberia, in
1908, leveling hundreds of acres of trees, was estimated at about
40
megatons, Draine said. If an asteroid that size fell on New York
City, "it
would kill millions of people," he said.
Astronomers say that, even with two close encounters in just over
a month,
there aren't more rogue asteroids out there. Rather, they are
better able
now to detect them.
"We're looking harder,'' Draine said Wednesday. "The
telescopes of projects
such as LINEAR in New Mexico and Spacewatch and Arizona are
finding things
we would have missed 10 or 50 years ago, things that have been
zipping
around the solar system for billions of years."
So, many scientists believe it is "desirable and wise"
to have networks of
astronomers surveying the skies and cataloguing as many orbiting
objects as
possible, he said. It was LINEAR - the Lincoln Laboratories
Near-Earth
Research project in New Mexico - that discovered asteroid 2002
NY40.
"So if there were to be something in the future with the
size and impact of
a Tunguska asteroid, we'll know in advance where and when it will
happen.
And if we have enough advance warning, we could at least evacuate
the area
and take precautions," Draine said. There might even be
time, he said, for
nations to unite and blast an incoming asteroid out of the skies,
the way
it's done in the movies, he said.
As the asteroid passes the Earth, scientists will be able to
better
calculate its orbit and return trip. Tracking agencies, such as
NASA's
Near-Earth Object Program, currently put the odds of it hitting
Earth on
Aug. 18, 2022 at about 1 in 500,000. This makes a chance of
impact
"extremely unlikely, but worrisome just the same,"
according to the Web site
for Sky & Telescope magazine.
But those odds also mean that "it's 499,999 times as likely
that we're not
going to be hit," Hally said. "That's very, very, very,
very, very close to
zero," he said.
Copyright © 2002 North Jersey Media Group Inc.
======================================
* OPINION & LETTERS TO THE MODERATOR *
======================================
(12) "AN ORGY OF MISINFORMATION AND CONFUSION CONCERNING
2002 NT7"
>From David Morrison <david.morrison@arc.nasa.gov>
NEO News (07/25/02) Confusion on 2002 NT7
Dear Friends and Students of NEOs:
As you probably all know, we are in the midst of an orgy of
misinformation
and confusion in the press, concerning asteroid 2002 NT7.
There have been "false alarm" stories in the past about
threatening
asteroids, some originating in poorly informed or misguided
statements made
by astronomers. The general pattern has been that a warning is
issued and a
day or two later retracted, reflecting either improved
calculations or new
data or both. It is entirely normal that a very low probability
prediction
of impact will go to zero as more information is processed. This
is not a
"failure" of the system, but
rather the normal working of the Spaceguard Survey and supporting
dynamical
calculations. However, the press sometimes portrays this as a
"mistake" by
astronomers. Consequently, most of us prefer to see no press
coverage of
such low-probability predictions. It was in this
spirit that no formal announcement was made concerning 2002 NT7,
since new
observations are accumulating and the whole situation is likely
to resolve
itself within a few days.
Unfortunately, the media themselves seem to have created the
current flood
of publicity surrounding NT7. Initial statements from the British
press
stated that 2002 NT7 was on a collision course with Earth with
the impact
predicted for February 1, 2019. The only qualification was that
the
prediction of an impact was still somewhat uncertain. There was
no hint of
the true situation, in which the probability of impact was at the
1-in-a-million level. As noted by Don Yeomans and others, the
position of
2002 NT7 on February 1, 2019, is actually uncertain by many
millions of
kilometers!
The situation has been made more complex by press references to
the Palermo
technical scale for classifying an asteroid risk. Astronomers use
this
Palermo scale in communicating among themselves, but several
years ago they
agreed to use the simpler Torino risk scale in talking to the
press and
public. The Torino scale was invented to facilitate such
communication. As
recently noted by Rick Binzel: The largest rationale for the
Torino Scale is
that we all have a common lexicon for communicating with the
public. If each
and every one of us would say: "That object is only zero (or
one) on the
Torino scale, meaning we are carefully monitoring it, with no
cause for
public concern." eventually the responsible press and
responsible people
would learn to categorize these "events" as being the
same as the last ones
that "just went away."
Below are two items: (1) a statement that I am sending to people
who e-mail
me expressing their concern that this asteroid will hit in 2019,
and (2) a
selection of the distorted initial press coverage in the UK taken
from Benny
Peiser's CCNet.
David Morrison
==========================================
NOTE TO CONCERNED CITIZENS
This newly discovered asteroid (2002 NT7) is very unlikely to hit
the Earth.
The current odds are a million to one against hitting. In any
case,
astronomers are continuing to measure its position, and within a
few days we
should know for sure what the circumstances are for 2019.
Meanwhile, the
story has been blown out of proportion. Statements from the press
that the
asteroid is on a collision course with Earth are simply false.
The probability of impact is so small that this asteroid remains
at a risk
level on the Torino scale of 0 or 1 - meaning that the chances of
impact
from another unknown NEA of the same size or larger is similar to
the
chances of being hit by 2002 NT7. However, the impact probability
is not yet
zero, and additional observations are needed to ensure that this
object will
not hit the Earth in 17 years.
Although 2002 NT7 is unlikely to pose any danger, the long-term
risk of
asteroid collision is real.
The Earth orbits the Sun in a sort of cosmic shooting gallery,
subject to
impacts from comets and asteroids. It is only fairly recently
that we have
come to appreciate that these impacts by asteroids and comets
(often called
Near Earth Objects, or NEOs) pose a significant hazard to life
and property.
Although the annual probability of the Earth being struck by a
large
asteroid or comet is extremely small, the consequences of such a
collision
are so catastrophic that it is prudent to assess the nature of
the threat
and prepare to deal with it.
Studies have shown that the risk from cosmic impact increases
with the size
of the projectile. The greatest risk is associated with objects
large enough
to perturb the Earth's climate on a global scale by injecting
large
quantities of dust into the stratosphere. Such an event could
depress
temperatures around the globe, leading to massive loss of food
crops and
possible breakdown of society. Such global catastrophes are
qualitatively
different from other more common hazards that we face (excepting
nuclear
war), because of their potential effect on the entire planet and
its
population. Various studies have suggested that the minimum mass
impacting
body to produce such global consequences is several tens of
billions of
tons, resulting in a groundburst explosion with energy in the
vicinity of a
million megatons of TNT. The corresponding threshold diameter for
NEOs is
between 1 and 2 km. Smaller objects (down to tens of meters
diameter) can
cause severe local damage but pose no global threat.
We don't know when the next NEO impact will take place, but we
can calculate
the odds. Statistically, the greatest danger is from an NEO with
about 1
million megatons energy (roughly 2 km in diameter). On average,
one of these
collides with the Earth once or twice per million years,
producing a global
catastrophe that would kill a substantial (but unknown) fraction
of the
Earth's human population. Reduced to personal terms, this means
that you
have about one chance in 20,000 of dying as a result of a
collision. Such statistics are
interesting, but they don't tell you, of course, when the next
catastrophic
impact will take place-next year or a million years from now.
How much warning will we have? With nearly half of even the
larger NEOs
remaining undiscovered, the most likely warning today would be
zero -- the
first indication of a collision would be the flash of light and
the shaking
of the ground as it hit. In contrast, if the current surveys
actually
discover a NEO on a collision course, we would expect many
decades of
warning. Any NEO that is going to hit the Earth will swing near
our planet
many times before it hits, and it should be discovered by
comprehensive sky
searches. This is the purpose of the Spaceguard Survey. In almost
all cases,
we will either have a long lead time or none at all.
Meanwhile, the Spaceguard Survey has already discovered more than
half of
the near Earth asteroids 1 km or larger, and we are on track to
find 90% of
them before the end of this decade.
For more information see the NASA websites:
<impact.arc.nasa.gov> and
<neo.jpl.nasa.gov>.
David Morrison
NASA Ames Research Center
==========
(13) YOU SAY TORINO - I SAY PALERMO: WHY BLAMING THE MEDIA WON'T
WORK
>From Benny Peiser <b.j.peiser@livjm.ac.uk>
Is the media to blame for "an orgy of misinformation and
confusion"
regarding the latest asteroid scare? According to David
Morrison's analysis
(NEO News 25/07/02) it would appear that this is the case. After
all, impact
risk assessors keep mum this time and "no formal
announcement was made
concerning 2002 NT7, since new observations are accumulating and
the whole
situation is likely to resolve itself within a few days." So
why has
asteroid 2002 NT7 been attracting such phenomenal interest from
news outlets
around the globe - and why the often inaccurate reporting?
For a start, it was the first virtual impactor announced by
NEODyS to have a
positive rating on the Palermo Scale for a virtual impact this
century. "So
what?" It still was rated only as a level 1 NEA on the
Torino Scale - and
that's all that counts in asteroid PR. Consequently, we should
have
emphasised the Torino Scale message exclusively, says Dave
Morrison: "If
each and every one of us would say: "That object is only
zero (or one) on
the Torino scale, meaning we are carefully monitoring it, with no
cause for
public concern" eventually the responsible press and
responsible people
would learn to categorize these "events" as being the
same as the last ones
that "just went away."
Sounds convincing - but it isn't. Basically, the
misunderstandings about NT7
were mainly due to lingering ambiguities and confusion about the
two
different impact risk assessment tools currently used by orbit
calculators
at JPL and Pisa University: The Torino Scale
(http://impact.arc.nasa.gov/torino/index.html)
and the Palermo Scale
(http://neo.jpl.nasa.gov/risk/doc/palermo.html).
As Morrison rightly states: According to the Torino Scale, a
virtual
impactor rated as a level 1 object merits "careful
monitoring, but no public
concern." Objects rated on this level have impact
probabilities below the
yearly background collision probability for objects in this size
category.
As far as the Torino Scale is concerned, only close approaches by
virtual
impactors that have higher collision chances than the Earth
typically
experiences over a few decades "merit concern", i.e.
Torino ratings 2 and
above.
The Palermo Technical Scale (http://neo.jpl.nasa.gov/risk/doc/palermo.html),
however, uses quite different terminology:
"Actual scale values less than -2 reflect events for which
there are no
likely consequences, while Palermo Scale values between -2 and 0
indicate
situations that merit careful monitoring. Potential impacts with
positive
Palermo Scale values will generally indicate situations that
merit some
level of concern."
In other words, while a Torino Scale 1 object does not merit
public concern,
an object that shows a positive Palermo Scale value "merits
some level of
concern." No wonder that most interested observers begin to
wonder what to
make of this rather unclear information posted on various impact
risk
websites.
It should have been obvious to everyone that the (first)
discovery of a NEA
with a positive Palermo Scale value for a virtual impact this
century would
generate public interest given the cautionary information posted
on JPL's
SENTRY website (http://neo.jpl.nasa.gov/risk/doc/sentry.html):
"To date, the risks posed by the potential impacts
identified by Sentry have
all been well below the background level, and hence, these events
have been
of academic or professional interest only, and not deserving of
great public
concern. Events with a Palermo Scale value greater than zero are
expected to
be very rare, but if one should be predicted, a Technical Review
of the
prediction would likely be requested from our colleagues in order
to verify
the calculations before the prediction is placed on the Risk
Page."
This statement not only calls specific attention to the fact that
virtual
impactors with a positive Palermo Scale value are highly unusual
("very
rare"). What is more, it makes clear that if such a NEA were
to be detected,
it would warrant the formal involvement of the IAU and "a
Technical Review
of the prediction would likely be requested."
Another reason, I guess, why 2002 NT7 attracted more attention
that it
deserves (apart from its large size and the relatively short
virtual
"warning time") is due to the silence about whether or
not such an IAU
Review actually took place. From what David Morrison states, it
would appear
that a decision was taken by the IAU and its Review Team not to
issue a
press release. I have no criticism about this decision. In
fact, I don't
think an official press release was warranted. Nevertheless,
since NT7
presented a 'novel' scenario, and in a way, a 'historic first',
it would
have been prudent to added clarifying information to the cryptic
data and
calculations on the impact risk pages regarding NT7. (As a matter
of fact, I
did ask JPL shortly after their excellent SENTRY programme was
launched what
would happen in case a positive Palermo Scale object were to be
discovered;
I was told that, in all likelihood, the data would be peer
reviewed and
explicatory information posted on the risk pages. I guess that is
what many
expected to happen). And indeed, additional information was
eventually
provided by JPL on 24 July (http://neo.jpl.nasa.gov/),
unfortunately only
*after* the story had already hit the various news agencies.
While this lack of expounding information contributed to some
uncertainties,
Kelly Beatty, I am pretty sure, was not the only one who seemed
confused
about an apparent "significant" difference between the
positive Palermo
Scale value announced by NEODyS and the negative PS value
published by JPL
(see letter further below).
Given all these technical problems and confusion of our own
making (not to
mention the minor confusion about differing impact probabilities,
ranging
somewhere from 1:60.000 to 1 in a million), let's not blame the
media for a
story poorly "managed" by ourselves. After all, almost
all reports written
by some of the most experienced science editors and reporters are
based on
the information given to them by more than two dozend of eminent
NEO
astronomers and researchers. Instead of blaming the media, let us
rather
focus on the unresolved home-made problems so that we can learn
some
constructive lessons from the 2002 NT7 events.
So, once again we are forced to address the inherent PR problems
of our
handling of the impact hazard in public (whether on impact risk
websites,
NEO mailing lists, press interviews or in any other public form).
In this
respect, I can find no better way to conclude my brief thoughts
than to
quote Brian Marsden's timely caution which he wrote just two
weeks ago in
CCNet (12/07/02):
"[The] two groups, at JPL and in Pisa, are routinely
carrying out the NEO
impact-probability computations with essentially identical
results. If there
were a significant and serious difference, then a review might be
in order,
but that is unlikely to happen. In fact, the whole review
discussion has
never involved a significant difference in computations from the
same data.
The review process need address only what is said, not what is
computed. And
what is said should be reviewed, not just by astronomers, but by
a group
with expertise also in many other disciplines."
Benny Peiser
26 July 2002
===========
(14) THE MEANING OF ASTEROID RISK LISTINGS
>From Jon Giorgini <jdg@tycho.jpl.nasa.gov>
Dear Benny,
Based on discussions with the press and others in the wake of
2002 NT7, it
seems NONE of the people I have talked to (no one outside the
"impact
community") understands the meaning of a listing on a risk
page. That is,
the difference between the "potential impacts"
and "predicted impacts".
Two or three weeks of optical data is not enough to conclusively
identify an
impact years in the future. POSSIBLE hazards can be flagged, but
these are
actually due to the lack of orbit knowledge; the asteroid could
be so many
places the Earth can't help but be in some of them.
These listings are POSSIBLE impacts, not PREDICTED impacts.
To PREDICT an asteroid's orbit reliably you need radar
measurements or at
least optical observations spanning 1 (preferably two) orbit
periods of the
asteroid. With an orbit period of 2.29 years, that means we
should be able
to usefully predict 2002 NT7's orbit in a positive way for a few
decades
after 2-4 more years of tracking it. By contrast, eliminating an
entry on
the risk page is a negative prediction; a prediction of where it
will NOT
be.
Results with less data -- 2 or 3 weeks or even months -- are
simply
astronomer's doing their routine, daily chore of eliminating
obscure
possibilities.
The listings are not really PREDICTIONS of impact, but a
statement that one
is POSSIBLE, primarily because it is not known for sure where the
asteroid
will be. Of course lots, of things are possible, most of which
will not
happen.
It's possible I will be on top of Mount Everest next month but I
am not
predicting it. And there will come a point when my being on Mount
Everest at
some instant can be positively excluded ("that's
impossible!").
The purpose behind the risk web page JPL produces is to
communicate
possibilities to other astronomers so they know which objects
require more
observations. A listing is not a declaration that an object is
predicted to
impact, or even come close to the Earth at that time, only that
the
possibility has not been ruled out.
As far as the public is concerned, it just isn't worth getting
worked up
over an object with a couple weeks of optical data showing a
possible Earth
encounter years from now. SOMETIMES, IT CAN'T EVEN BE SAID
FOR CERTAIN WHAT
SIDE OF THE SUN SUCH AN OBJECT WILL BE ON AT THE TIME OF THE
LISTED POSSIBLE IMPACT. A few days later, additional measurements
will
shrink the orbit uncertainty region by a relatively large amount
and the
Earth will fall out of the risk zone.
A pointer to such objects is valuable to astronomers however, so
they
can organize their limited resources to continuing tracking
objects with
POSSIBLE (but by no means PREDICTED) impact potential.
In general, it is very difficult for fuzzy optical measurements
to narrow
the uncertainties for newly discovered objects. A conclusive
impact
detection will almost certainly have to come from radar which can
measure
the position of an object to within a few meters. Optical
measurements
are typically good only at the 10's-100's of km level which
fuzzes out
knowledge quickly in a few years.
The only substantive hazard prediction out there is 1950 DA; 51
years of
optical data and recent radar data together indicate a possible
impact event
with odds between 0 and 1-in-300 on March 16, 2880.
Ground-based observers
could track 1950 DA for the next few decades without
substantially changing
the possibilities since the orbit uncertainties are so small they
are
dominated by the way the asteroid spins in space.
Regards,
Jon
Giorgini
|Navigation & Mission Design Section
Senior
Engineer
| Solar System Dynamics Group
Jon.Giorgini@jpl.nasa.gov
| Jet Propulsion Laboratory
=============
(15) DIFFERENT IMPACT PROBABILITIES?
>From Kelly Beatty <kbeatty@SkyandTelescope.com>
Benny...
has anyone besides me noticed that JPL and NeoDYS give
significantly
different impact probabilities and, perhaps more to the point,
negative and
positive (respectively) Palermo ratings?
Kelly
MODERATOR'S NOTE: Yes, I also noticed this discepancy. As I
understand it,
NEODyS and SENTRY are not identical systems. They use slightly
different
assumptions in the error analysis and they sometimes use slightly
different
data sets because of the data weighting schemes. Hence,
these minute differences in these uncertainty computations.
Although they
*appear* to be significantly different because of their different
Palermo
Scale values, the inherent accuracy of the computation programmes
at JPL and
Pisa both currently give 2002 NT7 a Palermo Scale of about zero
(background). BJP
============
(16) NEAR MISSES AND THE MEDIA
>From Charles Cockell <csco@bas.ac.uk>
Dear Benny,
By co-incidence I am writing to you from the Haughton impact
crater in the
arctic, where 23 million years ago a million megaton impact event
did occur.
But I'm interested by the article in the Times that makes light
of the
impact threat. The chances of a continent-scale devastating
impact are low
(perhaps once every 10 million years). The fact that they have
occurred is
not in doubt, the fact that they will occur is not in doubt. The
fact that
if we don't find a way to stop them we will eventually be doomed
is also not
in doubt.
However, it seems to me that the impact community will achieve
exactly the
opposite of what it intends if it spits out stories of
'near-misses'. There
are only so many of these that the media will publicise before it
gets bored
of the 'impact hazard' as a news item.
Publicising the fact that there are objects out there that could
potentially
do devastation if they were on the wrong trajectory is obviously
a good
thing and perhaps the best way to inform, but presenting them as
'near-misses', particularly when human civilization has not been
virtually
eradicated by them since its birth in Africa approx 3 million
years ago is
not going to go unnoticed by the media, hence the Times article.
It seems that to convince people of the need for planetary
protection a
strategy of informing people about the vast number of objects and
their
possible effects on Earth and the statistical certainty of impact
(whatever
that length of time might be) would be better than issuing dire
warnings of
near misses.
Charles
==============
(17) GERMAN TV: "10% PROBABILITY OF IMPACT"
>From Daniel Fischer <dfischer@astro.uni-bonn.de>
Hi Benny,
thanks for keeping us updated with the echoes of 2002 NT7! Some
German TV
stations also got crazy about it yesterday, with one reporting
that "the
impact probability is only [sic] 10 percent, which does not sound
like much
..." The most interesting side aspect of the whole affair
was a piece on CNN
International, though, in which science reporter Ann Kellen
(sp.?) promoted
solar sails as the best way to deflect a threatening NEA - I
wonder where
she got that idea from (as opposed to the more 'popular'
stand-off nuclear
weapon concept most everyone else is promoting).
Regards, Daniel
====================
IN OTHER NEWS ....
====================
(18) TRUE TALLY OF ASTEROIDS PROBABLY AT HIGH END OF ESTIMATES
>From Space.com, 23 July 2002
http://www.space.com/scienceastronomy/asteroid_tally_020723.html
By Robert Roy Britt
Senior Science Writer
The continued rapid pace of discovery for large asteroids in
relatively
close proximity to Earth suggests there may be more of them than
some
scientists have predicted. The speculation, from one of the
astronomers who
helps count the rocks, does not imply a significantly increased
threat to
Earth, but it does extend a long-running debate over just how
many of these
space rocks exist.
Large Near Earth Objects (NEOs) are asteroids bigger than 1
kilometer (0.62
miles) that loosely inhabit the region of the solar system
through which
Earth orbits. More than 600 of these large NEOs have been found.
Not a single one is known to be on a collision course with the
planet.
However, the big, Sun-orbiting hunks of metal and stone are of
great
interest to scientists because of the potential for one being
discovered
that could hit us down the road. Such an impact would cause
devastation on a
global scale, possibly pushing humans into a Dark Age existence.
Experts say
the scenario might be avoided by mounting a mission to deflect or
destroy an
asteroid known to be targeting us.
Various research groups from around the world have taken their
best shots in
recent years at calculating how many 1-kilometer and larger NEOs
are out
there. Estimates have ranged from 700 to 2,000.
Astronomers frequently cite 1,000 as the best estimate these
days. Another
popular count, however, is 1,200. Both prognostications are based
on
detailed studies and have error margins of plus or minus 100 or
200
potentially deadly giant boulders.
If either of the leading estimates is correct, then just more
than half of
all NEOs have been found.
To Brian Marsden, director of the Minor Planet Center where
asteroids are
officially catalogued, logic dictates that the pace of discovery
ought to be
slowing down, because there are now fewer NEOs that remain to be
detected
and hence the chances of finding each one is reduced.
But the pace has not slowed.
"Since the new discoveries are indeed still coming along at
about 100 per
year ... the number is probably not 1,000 minus anything, but
more likely at
least 1,200 or so," Marsden told SPACE.com.
If Marsden is correct, astronomers would not be overly surprised.
But his
logic does represent an unexpectedly simple method of suggesting
that the
lowball estimates are probably not correct.
Meanwhile, SPACE.com has learned of a new estimate. It comes from
NASA
researcher David Morrison and his colleagues and will be
presented in a
forthcoming book titled "Asteroids III" (University of
Arizona Press).
Morrison, senior scientist at the NASA Astrobiology Institute at
the Ames
Research Center, said via e-mail that it's "pretty clear
that the number is
not substantially less than 1,000." His team prefers 1,100,
plus or minus
100 -- which, Morrison points out, encompasses the possibility of
1,200
suggested by Marsden.
Alan Harris is a co-author of the chapter in "Asteroids
III" that deals with
the impact odds. Harris is also researcher at NASA's Jet
Propulsion
Laboratory, and he spends a lot of his time making and analyzing
these
estimates. Harris said the discovery rate continues to be high in
part
because detection methods have improved. It's very difficult to
know, he
said, how strong this effect is versus the possibility that there
are simply
more asteroids out there than expected.
"A population of 800 is implausible in the light of present
discovery rates
and the number already discovered," Harris said. One
thousand is plausible,
he added, as is 1,200. "I have to say though that I would be
less surprised
if the real population is greater than 1,200 than that if it is
less than
1,000."
Ultimately, the exact number is of little consequence. The
important thing
is simply whether or not one of them is headed our way.
Copyright 2002, Space.com
=======
(19) SCIENTISTS DOUBT CLAIMS OF INVISIBLE 'MIRROR' COMETS AND
ASTEROIDS
>From Space.com, 25 July 2002
http://www.space.com/scienceastronomy/mirror_matter_020725.html
By Robert Roy Britt
Senior Science Writer
Australian physicist Robert Foot thinks invisible asteroids have
bombarded
Earth in the past, unseen comets may be headed our way as you
read this. In
fact everything in the cosmos has a mysterious "mirror
matter" counterpart,
from stars to planets and even you.
Mainstream scientists are skeptical of the whole theory of mirror
matter. It
has been around for decades and is invoked by some to explain
"dark matter,"
an unobserved but significant amount of mysterious material that
scientists
say must exist based on the effects of gravity they observe in
galaxies.
Mirror matter theory holds that for each of the known basic
particles, such
as the electron, proton and photon, there is a distinct mirror
partner.
Because we are made of ordinary matter, the thinking goes, the
mirror
universe and its contents are invisible to us. But mirror matter
would have
mass, and so it would interact gravitationally with the
observable universe.
A handful of physicists around the world adhere to the idea.
"If mirror matter exists, then there should exist also
mirror stars, mirror
planets, even mirror life," says Foot, author of a new book,
"Shadowlands:
Quest for Mirror Matter in the Universe" (Upublish.com).
Mainstream scientists don't all rule out mirror matter.
"The idea of mirror matter is plausible, and as such it
should be looked
into," said MIT researcher John Arabadjis, who studies dark
matter.
"However, the evidence that has been used to support the
idea that mirror
matter actually exists in large quantities is, I think, very
flimsy."
Foot's latest defenses of the theory stretch plausibility beyond
what
Arabadjis and other researchers are willing to accept. In a
statement issued
this week by the University of Melbourne, where he works, Foot
claims that a
longstanding puzzle over "missing" comets could be
explained by mirror
matter.
Missing comets
For 50 years or so, astronomers have known that most comets come
from a
distant region of the solar system called the Oort Cloud. Theory
predicts
that more comets should make second trips through the inner solar
system
than what astronomers observe. In a recent issue of the journal
Science,
researchers said the best explanation is that the comets simply
disintegrate.
But Foot has another explanation. He said the missing comets
"could simply
be mirror comets with embedded ordinary matter. Once they have
passed the
Sun, their ordinary volatile components progressively burn off,
leaving an
invisible mirror-matter core. This would explain why so many
simply fade
away."
Harold Levison, of the Southwest Research Institute and lead
author of the
comet study published in Science, disagrees.
"The only reason I can see for invoking mirror matter here
is if we did not
understand what happened to the comets," Levison told
SPACE.com. "However,
we do. They disintegrate. It has been observed many times."
A photograph of just such an event, released earlier this week,
supports
Levison's view.
Exploding asteroids
Foot further claims that an infamous 1908 event in Siberia, an
explosion
that flattened thousands of acres of forest but left behind no
hard evidence
for the cause, involved mirror matter. All leading asteroid
experts believe
this so-called Tunguska event was caused by an asteroid that
exploded above
the surface, torn apart by atmospheric friction.
According to Foot, the atmosphere could cause heat to build up
within a
mirror asteroid, causing it to explode and making it visible,
though no
ordinary matter would be left behind.
He also cites an event reportedly observed in Jordan in April
2001. A ball
of light was said to streak across the sky at low altitude, break
in two,
and then slam into a hill. Local astronomers found scorched trees
but no
crater.
"These events cannot be explained in terms of a space body
made of ordinary
matter," Foot said. "If the Jordan space body was made
of ordinary matter it
should have lit up a large part of the Middle East. This was not
observed."
He goes on to suggest that tons of mirror matter might lie hidden
just below
the surface of these sites, waiting to be found. Mirror atoms
could be
sorted out in a centrifuge, he says.
Levison doesn't think there are any mysteries to look into in
Jordan or
Tunguska.
"It is well known and modeled that small, normal, rocky or
icy impactors
will disintegrate in the atmosphere before they strike the
surface of the
Earth," Levison explained. "These small objects can be
moving fast enough
that they cause a huge explosion at high altitudes without
leaving a crater.
I really don't think you need to invoke strange physics to
understand the
astronomical phenomena described" by Foot.
Until and unless the mystery of dark matter is unraveled,
however, mirror
matter theory is not likely to go away. And though it might not
be needed to
explain missing comets or mysterious explosions, there could be
something to
it.
Physics can be strange, points out Arabadjis, the MIT researcher.
When Paul Dirac used math to predict in the 1920s that basic
particles have
associated antiparticles, the idea "was so unbelievable to
him that, well,
he refused to believe it at first," Arabadjis said. Later
experiments
detected these antiparticles (though most scientists do not
believe
antimatter equals or begets mirror matter).
And over the past few years, astronomers have realized that the
universe's
expansion is actually accelerating, something Arabadjis calls
"a truly
bizarre result" that can't be explained. Exotic "dark
energy" has been
proposed as a possible repulsive force behind this mystery.
"To be fair, physics sometimes produces really bizarre
answers," Arabadjis
said.
Copyright 2002, Space.com
============
(20) AND FINALLY: 10 WAYS TO BEAT ARMAGEDDON :-)
>From The Sun, 25 July 2002
1. Dig yourself a very, very deep hole thousands of feet below
the Earth's
surface and build a super shelter. Or simply reinforce the house
from Big
Brother 19 with concrete and use that as a bunker.
2. Join the latest amateur attempt to build a space rocket from
scratch
-now. At least you have 17 years to tinker with the engine to
make sure it
doesn't break down.
3. Tie one end of Jordan's bra to Big Ben and the other to Canary
Wharf and
catapult the massive asteroid back where it came from.
4. Start saving for a one-way ticket to a space hotel which will
probably be
orbiting the Moon by that time.
5. Try to befriend an Extra Terrestrial - and then do your best
to bribe the
friendly alien to shuttle you off the doomed Earth and back to
the safety of
its home planet.
6. Find out exactly which continent the asteroid is going to hit
- and make
sure you and your family have not booked your holiday there.
7. Get Manchester United's £29.1 million signing Rio Ferdinand
to justify
his out-of-this-world transfer fee - and head it back into space.
8. Book a round-the-world plane ticket and hope you are in the
air to avoid
the worst when it hits.
9. Bounce it off the Millennium Dome - with any luck we might
menage to get
rid of two disasters in one go.
10. Retrain as an astronaut and hope you are on a mission to a
far distant
galaxy when the rock collides with Earth.
Copyright 2002, The Sun
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*
BLAME FOR NT7
From David Whitehouse <dr_d_whitehouse@msn.com>
Dear Benny,
Once again, some in CCNet are blaming the media for the 2002 NT7
story.
Why?
I have read most of the reports about NT7 and the majority of
them have
been accurate in reporting the situation regarding this now
famous rock.
Most reports said, quite rightly, that, based on the limited data
available, it had an impact solution in 2019, but that more
observations
would almost certainly rule out any collision. I cannot agree
that the
vast majority of the reports give "no hint of the true
situation," as
one astronomer has commented.
Indeed, the vast majority of reports contain accurate quotes from
a
handful of experts, yourself included, placing the situation in
the
correct context.
It is true that some outlets have been irresponsible, albeit
sometimes
obviously light-heartedly so, but that is life and that happens
in all
subjects.
Scientists should learn from the politicians who have this sort
of thing
all the time - it doesn't matter - don't take such reports too
seriously. Besides if you want governments to take this situation
more
seriously, and provide more funding, such stories are good, you
could
say..ahem...heaven sent. Use them. You should be glad of such
coverage.
It is also inevitable in such a story, as indeed in many others,
that
some outlets will deliberately take a counter view to the
original
reports, especially if they did not cover the story in the first
rush.
The fact that NT7 was the first positive Palermo scale event was
a news
story and anyone savvy with the media would have recognised it as
such
and set about to manage the situation so as to get the best from
it, as
they saw it. It strikes me that the Torino scale did not fulfil
its
purpose this time.
This is a subject of mixed messages as far as the media are
concerned. I
have seen many comments from astronomers and Nasa saying (after
they had
criticised the media) that NT7 will not hit us but then adding
such
phrases as "ALMOST no chance" and "the impact
probability is NOT ZERO"
and "there is a GOOD chance that this particular object
won't hit us" -
actual quotes. Journalists can drive a cart and horses between
ALMOST
and NOT-ZERO. Ask the politicians about it.
Regards,
David.
David Whitehouse, Science Editor BBC News Online.
*
ANOTHER TABLOID TAKES THE MICKEY OUT OF 2002 NT7
Today's Editorial from The New York Times, 26 July 2002
http://www.nytimes.com/2002/07/26/opinion/26FRI4.html?ex=1028347200&en=e511c8a0f342f313&ei=5040&partner=MOREOVER
Thank goodness! Another killer asteroid is on the way, just in
time to take
our minds off the stock market and foreign affairs. Asteroids, in
fact, are
just about the perfect peril - a lot less scary than a close
encounter with
a shark and a lot more reliable than Saddam Hussein.
The latest asteroid menace goes by the uninspiring name 2002 NT7.
It was
detected two weeks ago by a surveillance system designed to give
early
warning of any errant rocks in our neighborhood. This particular
rock is
about 1.2 miles wide and is cruising around the sun in a highly
inclined
orbit that comes extremely close at one point to our own
planetary orbit.
The Earth will reach that intersection less than 17 years from
now, on Feb.
1, 2019. If the asteroid gets there at the same time, it would be
analogous
to a train and a car colliding at a grade crossing.
The impact would be nowhere near as awesome as the collision 65
million
years ago that kicked up so much dust it wiped out the dinosaurs.
But even
if the asteroid simply dug a very big crater, that is surely
enough to
warrant some shivers of anticipation.
Most of the astronomers who comment on these things have been
playing down
the likelihood of collision, noting that the asteroid could well
be many
millions of miles away when Earth passes the intersection. Some
say the
chances of NT7's hitting us are less than one in 200,000, or
maybe even one
in a million. But no one can be sure until the rock is watched a
bit longer,
allowing more precise calculations of its path.
Meanwhile we are free to worry away at our leisure. It's a lot
more fun than
fretting every time Tom Ridge or John Ashcroft warns us that
terrorists are
out to do us in, at a time and place unspecified. At least with
asteroids,
those who issue the warnings know where the terror rock is and
can calculate
where it is headed.
Copyright 2002, The New York Times